$9km + 5l - m - 8 = l + 4m - 1$ Solve for $k$.
Combine constant terms on the right. $9km + 5l - m - {8} = l + 4m - {1}$ $9km + 5l - m = l + 4m + {7}$ Combine $m$ terms on the right. $9km + 5l - {m} = l + {4m} + 7$ $9km + 5l = l + {5m} + 7$ Combine $l$ terms on the right. $9km + {5l} = {l} + 5m + 7$ $9km = -{4l} + 5m + 7$ Isolate $k$ ${9}k{m} = -4l + 5m + 7$ $k = \dfrac{ -4l + 5m + 7 }{ {9m} }$